1. Technical Field
The present invention relates to a technology for dividing one field into a plurality of sub-fields and for representing gray-scale levels by turning on or off pixels in each sub-field.
2. Related Art
When gray-scale display is to be performed in an electro-optical apparatus in which display elements such as liquid-crystal elements are used as pixels, the following technology has been proposed in place of a voltage modulation method. That is, a technology has been proposed in which one field is divided into a plurality of sub-fields, a pixel (liquid-crystal element) is turned on or off in each sub-field, and the ratio of the time period in which a pixel is turned on to the time period in which a pixel is turned off in one field is changed, thereby performing gray-scale display (see JP-A-2003-114661).
Furthermore, in the above-described technology, by using the fact that the response speed of a liquid-crystal element is comparatively slow, in more detail, by using the fact that, even if a liquid-crystal element is turned on in only one sub-field, the reflectance (or the transmittance) of the liquid-crystal element does not immediately reach a numeric value corresponding to an on state (does not saturate), the transmittance or the reflectance of the liquid-crystal element can be finely controlled.
In general, the response speed of a liquid-crystal element increases with temperature. When a state is reached in which temperature is high and the response speed of a liquid-crystal element is high, the assumption that the reflectance of the liquid crystal when the liquid-crystal element is turned on does not immediately reach a numeric value corresponding to an on state does not hold. For this reason, a problem that suitable gray-scale representation cannot be performed has been considered.
Furthermore, when the same gray scale is to be shown over a wide range of pixels, these pixels are turned on/off in the same manner, and therefore a problem of noticeable flicker has been pointed out.